1. Field of the Invention
The present invention relates to laminar flow control apparatus for aerodynamic surfaces, and more particularly to an apparatus adapted to be mounted on an aircraft structural surface, such as a wing or fuselage, to interact with fluid flowing over the structural surface in such a manner as to stabilize turbulent fluid flow at the surface and thereby produce very efficient flow of the fluid over the aircraft surface.
2. Background of the Invention
The technique of controlling a mainstream of ambient fluid moving across aerodynamic surfaces has been known for some time. This technique is known as laminar flow control (LFC), and is important for eliminating undesired drag and turbulence in the immediate vicinity of aerodynamic working surfaces. Generally, a secondary fluid stream under pressure is caused to pass through pores in an aerodynamic working surface. The pressure field created by the secondary fluid impinges on a mainstream of ambient fluid flowing over the surface, and has the effect of altering behavior of the mainstream fluid flow, most desirably of causing the mainstream of fluid to be entrained closely along the working surface.
Significant advantages accrue from using laminar flow control techniques In aerodynamic vehicles, including significant reductions in total overall gross weight, fuel burned and engine size. Laminar flow control in these vehicles can be useful at supersonic, as well as subsonic, speeds.
In supersonic aircraft or in spacecraft, it would be highly desirable to achieve 50% to 60% chord laminar flow on a highly swept wing with an advanced pressure distribution across the wing at supersonic speeds.
A typical aircraft laminar flow control wing panel comprises a multi-layer, reinforced structure including inner and outer skins and one or more internal reinforcing members bonded at selected regions to the inner and outer skins. The panel skins are on the order of 0.025"-0.040" thick, are hot-formed to assure excellent aerodynamic surface quality, and are laser drilled with hole-spacing tailored for optimum suction distribution.
Factors which influence design of laminar flow control wing panels include the pressure distribution over the region to be laminarized, skin perforation patterns, size and spacings, and internal flow requirments. Control of this last factor influences the suction distribution required over the suction surface for a range of design and off-design conditions, as well as the outflow from the suction surface and pressure loss through the internal flow passages.